docs: def getParser():
      "Creates and returns the argparse parser object."
      parser = argparse.ArgumentParser(formatter_class=argparse.RawDescriptionHelpFormatter,
                                       description=__description__)
      parser.add_argument('output', help='Target volume.')
      parser.add_argument('inputs', nargs='+', help='Source volume(s).')
      parser.add_argument('-o', '--operation', dest='operation', choices=['sum', 'avg', 'max', 'min'], default='avg', help='Combinatorial operation to conduct.')
      parser.add_argument('-v', dest='verbose', action='store_true', help='Display more information.')
      parser.add_argument('-d', dest='debug', action='store_true', help='Display debug information.')
      parser.add_argument('-f', dest='force', action='store_true', help='Silently override existing output images.')
      return parser